Dissoluble wall structure



June 24, 1969 E. LABORDE ETAL DISSOLUBLE WALL STRUCTURE Filed March a,1966 awn/mes EMILE LRBORDE EnN Z/LBGEMRA/ United States Patent 3,451,913DISSOLUBLE WALL STRUCTURE Emile Laborde and Jean Zilberman, Paris,France, assiguors to C.I.T.-Compagnie Industrielle desTelecommunications, Paris, France Filed Mar. 3, 1966, Ser. No. 531,593Claims priority, applicati7on France, Mar. 3, 1965,

7, 98 Int. Cl. C23b 1/02 US. Cl. 204-248 7 Claims ABSTRACT OF THEDISCLOSURE The present invention relates to a device susceptible tobring about the piercing of a wall of a body floating on a liquid aftera duration of immersion comprised within certain limits.

There exist certain cases in which a three-dimensional body is intendedto float on a liquid, then at the end of a certain time, to lose itsfloatability and to sink to the bottom. This is the case in particularwith certain carrier apparatus for detection devices whose role is tofloat on the ocean during a certain time and thereafter to sink to thebottom at the end of some hours of operation of said devices,

There are already known in the prior art means to cause a body floatingon the ocean to lose its floatability, particularly by way ofdissolution or by way of electrochemical corrosion. In the first case atleast one dissolvable plug or stopper, constituted, for example, by amineral salt, is inserted into an aperture made into the enclosure belowthe water line. The nature of the product and the dimensions of theaperture are chosen in such a manner that the dissolution takes placefrom one side to the other, i.e., through and through at the end of atime, which, taking into consideration the variations of the parameterssuch as temperature of the water, degree of salinity, is comprisedwithin the prescribed limits, for example, between 3 and 30 hours. Onemay also realize an element or portion of the wall constituted by asmall plate of a first metal on which is deposited, preferably byelectroplating, a layer of a second metal susceptible of forming withthe first metal a galvanic couple. In the presence of the conductive seawater, the small plate and the metallic layer behave like an electricbattery, producing a certain current giving rise to an electrolyticattack of the plate which leads finally to the piercing of the wall.

Such a small plate may be obtained in an advantageous manner, forexample, by a deposit of gold on zinc.

However, experience has demonstrated that such a battery element formedby a plate of a metal covered by another plated metal, exposed to thesea water, has a tendency for the so-called passivation phenomenon bythe formation of compounds insoluble within the medium and electricallyinsulating, which enclosure or surround the surface, thereby increasingenormously the internal resistance of the cell, and slowing down thespeed of dissolution. An extreme dispersion of the piercing durationresults therefrom which may even exceed the maximum admissible limit.

This is the reason why, according to the present in- 3,451,913 PatentedJune 24, 1969 vention, a wall element intended to constitute an assemblyto be pierced by immersion into the sea comprises two metallic parts ofdifferent metal, separated by an insulating medium and connectedexternally by a conductor. In this manner, the electrolysis takes placeregularly and furnishes, with a dispersion of the duration reduced to aminimum, the desired piercing of the wall.

Accordingly, it is an object of the present invention to provide afloating structure of the type described above which eliminates bysimple means the shortcomings and drawbacks encountered with the priorart constructions.

It is another object of the present invention to provide a wallstructure for a floating body which assures the dedesired termination ofthe floata'bility thereof within the given time limits after immersioninto the salt water of the sea.

A further object of the present invention resides in a dissolvable wallstructure for a floating body which is not only simple in constructionand reliable in operation but which also assures proper functioningthereof within the given time limits.

These and further objects, features, and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawing which shows, in thesingle figure thereof, for purposes of illustration only, one embodimentin accordance with the present invention, and where- 1n:

The single figure is a partial cross-sectional view through a floatingbody provided with a dissolvable wall structure in accordance with thepresent invention.

Referring now to the single figure of the drawings, ref erence numeral 2designates therein a portion of a wall of an enclosure or vessel capableof floating. The bottom of the wall 2 comprises an aperture in theembossment or recess 3 thereof, formed "by a galvanic element comprisinga plate 1 of a first metal or alloy and a counterplate 4 through whichis pierced a central opening or aperture, made of a metal or alloydilferent from the first metal and presenting another oxidationpotential. The plate 1 and the counterplate 4 are spaced from one another by an insulating layer or element 5 extending over the entire orat least a portion of the mutually facing surfaces; the plate 1 and thecounterplate 4 are in electrical contact along the externalcircumference by the intermediary of a conductor 6. To avoid thecorrosion of the plate 1 during storage, the em'bossment or recess 3accommodating the galvanic element in accordance with the presentinvention is sealed by an impermeable or water-repellent skin or cover 7having an annular adhesive zone adhering to the external surface of thewall 2. The skin or cover 7 which will be torn off at the moment of useof the apparatus may be made of rubber or a flexible synthetic plasticresin of any known nature.

In the presence of a conductive liquid, for example, saline water of theocean, an electric battery is constituted thereby with the plate .1 andthe counterplate 4 as electrodes connected by an external circuit formedby the conductor 6 which may be in the form of an annular shapedconductor welded to the peripheral edges of the plate 1 and thecounterplate 4.

The substances forming the electrodes of the battery thus constitutedare chosen in such a manner that the polarity of their couple is suchthat there will be corrosion of the electrode formed by the plate 1.

In one preferred embodiment of the present invention, the plate 1 ismade of magnesium and the counterplate 4 of zinc.

1f the wall 2 of the enclosure is metallic, the metallic substancesforming the elements 1 and 6 are chosen in such a manner that the elfectof the difl'erent galvanic couples created with the metal of the wall 2reinforce the piercing effect of the galvanic element described hereinabove.

When the corrosion has taken place over the entire thickness of theplate 1, the wall of the enclosure becomes perforated.

The insulating material 5 is chosen in particular for itswater-repellent properties in order that its surface resistivity islittle sensitive to the moisture of the air in the normal storagecondiions and that thus no galvanic corrosion takes place prior toactually putting the device into service. It may be of anynon-hygroscopic, insulating substance, in particular, Mylar. Itsthickness must be sufiicient in order that the metallic surfaces facingeach other are effectively insulated.

The skin or cover 7 may be, for example, of polyethylene.

A wall equipped with a surface element according to the presentinvention presents a duration of the piercing which can be readilyreproduced for the same value of parameters. This duration varies as afunction of the temperature and conductivity of the liquid medium, andin particular, of the degree of salinity of the ocean water, in the mostfrequent case of application in which the enclosure to be pierced floatson the ocean.

While we have shown and described one embodiment in accordance with thepresent invention, it is understood that the same is not limited theretobut is susceptible of numerous changes and modifications as known to aperson skilled in the art, and we therefore do not wish to be limited tothe details shown and described herein but intend to cover all suchchanges and modifications as are encompassed by the scope of theappended claims.

We claim:

1. A metallic structure capable of being destroyed by a continuouscontact with an electrolyte, comprising:

afirst substantially circular metallic plate structure,

a layer of insulating material disposed over a substantially annularsurface of said first plate structure,

a second annular plate structure of a metal different from said firstplate structure, said second plate structure being disposed on saidlayer of insulating material so that mutually facing surface portions ofsaid first and second plate structures are separated by said insulatingmaterial, and a substantially annular shaped conductor means connectedto said first and second plate structure along their peripheral edges.

2. The combination according to claim 1, wherein said first platestructure is made of magnesium, said second plate structure of zinc, andsaid insulating material is non-hygroscopic.

3. The combination according to claim 1, wherein said conductor means iswelded to said first and second plate structures along their peripheraledges.

4. The combination according to claim 3, which further includes aremovable cover means disposed over said second plate structure topreclude an electrolyte from contacting said first and second platestructures and said conductor means until said cover is removed.

5. A metallic structure capable of being destroyed by a continuouscontact with an electrolyte, comprising:

a substantially circular magnesium plate structure,

a layer of non-hygroscopic insulating material disposed over asubstantially annular surface of said first plate structure,

a substantially annular zinc plate structure being disposed on saidlayer of insulating material, the periphery of said zinc plate structuresubstantially following the periphery of said insulating material andsaid magnesium plate structure, and

a substantially annular shaped conductor means connected to saidmagnesium and zinc plate structures along their peripheral edges.

6. The combination according to claim 5, wherein said conductor means iswelded to said magnesium and Zinc plate structures along theirperipheral edges.

7. The combination according to claim 6, which further includes aremovable cover means disposed over said zinc plate structure topreclude an electrolyte from contacting said Zinc and magnesium platestructures and said conductor means until said cover is removed.

References Cited UNITED STATES PATENTS 1/1961 Skinner 136- 3/1967Suleski 204-196 US. Cl. X.R.

